Conventional winding structures of a rotating electric machine are for example disclosed in Japanese Patent Laying-Open Nos. 2000-217290 and 03-178536.
Japanese Patent Laying-Open No. 2000-217290 discloses an electric motor in which windings of each phase are connected in the manner that windings opposite to each other in the radial direction are connected in parallel and a set of thus parallel-connected windings is connected in series with another set of parallel-connected windings.
Japanese Patent Laying-Open No. 03-178536 discloses a connection method for windings of a rotating electric machine, connecting parallel circuits each comprised of two series circuits.
In some cases, a rotor and a stator of a rotating electric machine are disposed eccentrically with respect to each other, namely respective centers of the rotor and the stator do not coincide. Here, in a winding structure in which series-connected coils are connected in parallel with another series-connected coils (like the winding structure disclosed in Japanese Patent Laying-Open No. 03-178536 for example), imbalance in electromotive force due to the eccentricity could generate cyclic current in the parallel circuit to accordingly cause increases of vibrations and noise of the rotating electric machine while it is driven.
However, in the case where parallel circuits are formed for each coil as disclosed in Japanese Patent Laying-Open No. 2000-217290, the coil-to-coil wire providing connection between coils is longer. Accordingly, the coil end increases in size.